Induction electric furnace



Sept. 20, 1932. o. J. BLANCHE-:T 1,878,458

' INDUCTION EIECTRIC FURNACE Filed Dec'. 16, '1930 2 Sheets-Sheet l 15 J4 5 V rsf m n fis )6 [Welder auf@ Jep km0/zeg f@ /v Sept. 20, 1932. o. J. BLANcHr-:T 1,878,458

INDUCTION ELECTRIC FURNACE Filed Dec. 16. 1950 2 Sheets-Sheet 2 Patented Sept. 20, 1932y I PATENT oEFlcE ovina JOSEPH BLANCHE@ oENEw nnnroanQMassacH/Usnr'rs INDUCTION ELECTRIC IUBNACE Application 111er! December 18, 1930.. Serial No. 502,693.

My invention relates to devices for heat treating the shanks of drills .and other like tools after hardening.

The main purpose of my invention is to anneal the shank of a drill .\or other like tool without discoloration;

A further purpose is to anneal drill Shanks, etc. in a non-oxidizing atmosphere.

A further purpose 1s to trap a non-oxidizing atmosphere in an annealing chamber and to insert and remove the drills to be annealed in such a Way as to cause a minimum release of or interference with this atmosphere.

A further purpose is to automatically time the heating and cooling times of drills, etc. during annealing so as to keep the heat on during a proper annealing period and to `reliably cool before removal from the chamoer.

Further purposes will appear in the speci- `lication and in the claims.

l have preferred to illustrate one main orm only, among the various forms in which any invent-ion may appear, selecting form which While practical and elicient, has been selected primarily because it Weil illustrates the principles of the invention.

the drawings Figure 1 is a diagrammatic illustration of my invention showing the furnace and timing mechanism inside elevation.

\Figure 2 is a vertical section partly broken away and omittin intermediate arts of all of the heatin 'coi s but one of t ose which comprise the urnace.

Figure?) is an enlarged fragmentary longitudinal section of a portion of a. furnace showing a single coil and the holder for a single drill in vertical position.

Figure 4 is a broken vertical cross section of a portion offa furnace showing the furnace l anddrill holder tilted.

Figures 5, Gand 7 are diagrammaticperspectlves of mechanism for controlling application of heat to the furnaces. l

In the drawings similar numerals indicate likeparts. i

, The problem to be met and the solution of the problem are so aptly illustrated by explaining conditions found in the art of maktheir sale.

through coils 12 supplied with hig ing drills and particularly in the of making high speed twist drills that'the invention will be described in terms of drill manufacture and treatment with the understand-A ing that it is intended to apply wherever similar conditions of discoloration'occur and prove objectionable.

In the manufacture of drills there is con.

siderable warping of the drills during the tempering. This occurs with all steel drills but the Warpinl is greater andvthereforel is more objectiona le with the alloy steels used in high speed drills than in so-called carbon steel drills and the necessity for grinding the drills to true them is more imperative with the high speed drills.

The grinding must be done after temper-- ing and takes the name oil the shank. The

name cannot well be replaced Without first c sirable immediate use in annealing Without leaving any discoloration.

My invention contemplates heat treatment I within a protected compartment or chamber and within a protective atmosphere, maintaining the drills within the atmosphere not only during the heating, but also during the cooling incident to the annealing process.

Describing the mechanism i'nfgeneral form, I show in Figure l a furnace 10 of which one possible form is shown in Figure 2 in connection with a drill holder 11 capable of y movement toward and from the furnace. I prefer to heat by high frequenc induction li frequency from a generator 13 through a transformer 14. Across the secondary coil is thrown a capacity 15 and a gap, which may be a quench gap, is inserted at 16. The current is controlled by any sixitable mechanism 17 whereby the current is cut off or is reduced after suitable time for heating. This mechanism,

My invention finds its most dec shown without detail in Figure 1, may be electrically or mechanically controlled.

It does not matter from the standpoint of my broad invention whether the control be by hand or automatic, and if the latter a time function, such as is edected by a clock or through revolving contacts, or an energy function as through an integrating watt meter, nor whether the time be tiXed to agree with the` needs for a large number of pieces of the same heat capacity or variable.

The frequency used and the voltage may both bel Varied greatly, subject to variation of course in the time required for the operation and the frequency ditfering according to the minimum size oi control to be treated as taught by Dr. Northrup in his U. S. Patents Nos. 1,694,791 and 1,694,792. While I deem my duty under the statute to give the best form ot this known to me l do not wish to be held to any figures on this question nor even to the frequency and voltage being of the same order as tried out by me, as l consider my invention broader than this and believe that easy tests will determine the voltage and Jfrequency best adapted to heating of individual pieces of work without the necessity even of computation such as has been rendered available by Dr. Northrup. Eperiments have shown that both the freqnency and the voltage can be quite high, very successful operation being secured at 50,000 cycles and 25,000 volts supplied from mains 18, 18 having a di'erence of potential of 220 volts.

The coils l2 may be water cooled, as is well known in the coreless induction heating art, and have intended to suggest this by the use of hollow tubing "i9 to which the electric current is connected as at 20 without interfering with the water cooling connections. As the connections for. this purpose are well known l have not considered it necessary to illustrate this water cooling attachment.

yThe coils are preferably enclosed within electrically insulating walls 21 surrounded by a heat insulator 22 so as to reduce electrical and thermal leakage to a minimum.

Though my invention can be applied and is quite effective in single units intended to treat one drill shank onlyA at a time there is considerable advantage in'speed of handling and the cheapness of operation in providing -the furnace withy a plurality of treating chambers and treating coils so that a eoi'-,

responding number of gang of drills may be treated at the same time. For convenience of illustration have shown five such compartments,coils and drills, the interior portions o the coils being omitted in Figure 2 from four of the iivecoils and in Figure 4 from the only coil shown. t

At the mouth of each compartment I may provide a seal, very conveniently effected by an asbestos ring 23which engages with the surface 24 of the drill when the drill shank 25 lies within the compartment. There is normally a further protection against gas leakage at this point by engagement of the surface 26 of the drill holder against the surface 27 of the furnace unit.

Through any suitable piping 28 communicating with the several compartments I fill them with a non-oxidizing atmosphere such as nitrogen and mount the furnace in such a position that the atmosphere will be trapped in the compartments. For an atn'lospherc lighter than air the openings 29 for drill entry will be located at the lower end ot the furnace. Two positions of the furnace are provided for in the drawings, the one the position of Figures 2 and 3 where the turnace lies with the axes of the treating chambers vertical and the other, shown in Figure 4, where the drill aXes are inclined, the purpose being in either event to protect against serious leakage of the oxidizing atmosphere through the apertures providing for drill insertion.

l have not considered it necessary to illustrate the drill holder in detail. The type used for my tests has been of extremely simple form as a clamp divided along a plane through the axes of the drills.

The nonoxidizing `atmosphere is furnished from any suitable tank 30 and is controlled by valve 3l, the pressure being indicated by a gauge 32.

While with nitrogen as the special atmosphere I locate the furnace so that its openings for drill insertion lie in the lower part of the furnace, if a heavier-than-air atmos Ehere be used these openings would or" course e located in the upper part ot the furnace and the drills would be inserted from above.

One convenient time regulator for determination of the time during which the current shall be applied and also the time during which the current shall be cut oli for cooling purposes is shown in Figure 5. In it the electromagnets 83 and 34 are arranged at the end of a plunger chamber within which an armature is free to move guided by a rod 36. The opposite end of the rod carries a plunger '37 which operates in an oil cylinder 38 and in which leakage is provided through oraround the piston so that tthe piston and oil cylinder are eifective as a dash-pot to retard movement of the plunger.

The electromagnets are supplied at 39, 40, 41 through switches 392,392 and 402 with current from a low tension source such as the individual 110 volt parts making up the 220 volt. supply. The electromagnets arey successively engaged and opened by a series of contacts'42 and 42 upon continuously rotatling contact'discs. The engagements of contacts 42 and 42', both shown as connected with the neutral 40, with brushes 43, 44 for electromagnets 36 and 37 are timed to lao alternate, with or without a time gap between contacts for the different electromagnets. Obviously the relative tlmes and lengths of time of excitation of the two electromagnets may be designed to oil'er lany .time relation between them by varying the an lari relative extensions ofthe contacts 42 an 42'. `The relative strengths of the electromagnets are also capable of adjustment by the use of rheostats 45 and 46. ,f

The o eration' of the plunger makes and breaks t e' high frequency circuit by an)1 suitable means of which I have diagrammati- ,cally illustrated a contact 47 carried by the plunger and connected with one side of the circuit as engaging lduring a part of the stroke of the plun er with a contact 48 connected with the ot er side of the circuit and s ring pressed at 49 to maintain engagement tiirough a part offfthe movement of the plunger. A

The contacts and contact interruptions ma be made unequal in time to any extent desire even where there is equal time of energization of the electromagnets, by varying the extent of follow of the contact 48 to maini ta'in engagement with contact 47 so that this fu nishes another means whereby an interruption in line 50, 51 may be opened or closed theinterruption in line 50, 51.

A motor 52 through any suitable gear reduction 53 and change speed device 54 .ro-

tates a contact arm 55, connected with portion.

50 of the line, so that this arm Will en' age contacts A56 connected with the part 51 o the The angular length of the contacts 56 and 1 their number per rotation-whether one or many-combined with the speed change mechanism 54 afford a wide range of adjustment in the timing provided. Of these two adjustments variation in the angular length of the contacts 56 affects the relative length of time for heating andvfor cooling and replacement, but variation'bv change of the speed adjustment 54 alters both of these times in equal-proportion.

My discussion of time variation is not intended to indicate that it is necessary to vary the time in 'actual practice. IVhere a fur` nace is roperating upon products of the same character-such as drills-and particularly Where these products are nearly of the same size, a standard timing may readily be deter.

mined upon and the apparatus will then be designed for thistiming Without lneed of variation. Ihe contact mechanisms shown are,

of course, fully operative for, such a condition and in order to emphasize this I have illusv ydiagrammatic in that they show examples only of mechanism by which the function ma be carried out and without intended restriction to the particular forms shown.

Inoperation on the drills, the chambers or compartments are filled with the protective gas,l the drill holders are loaded and the shanks of all the drills are inserted within the openings so that the shanks extend into the treating compartments to any desired extent. The extent can be preliminarily determined by the structure ofthe holder or can be set by an adjustable extent of projection of the drills outside of the holder. Any suitable guides not shown may be used to ensure registration of the drill Shanks with the chamber openings.

The current is turned on by hand or byany operating mechanism and is4 maintained on during the heating part-0f the annealing operation. The current is then turned oi, the drill shanks are allowed to cool in the protective'atmosphere and the drills are'removed for insertion of a new set of drills.V The supply of nitrogen will be but little dis, sipated and any slight dissi ation of the nitrogen may be replaced by a urther supply from the tank. \0

' In view of my inventi n and disclosure vari'ations and modifications to meet individual whim 'or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention what I claim 'as new and desire to secure by Letters Patent is: I

1. In a tempering device fortools, the combination of a high frequency coreless inductor 'coil furnace, heat insulation about the furnace and a non-oxidizing atmosphere Within the coil and inthe space for the tool,

lthe opening for insertion of the tool into the atmosphere being so located as to retain the atmosphere Within the space by difference in density between the non-oxidizing atmosphere and the air. i 2. In a tempering furnace for tools, a coreless inductor electric furnace coil having a space within the coil for insertion of a tool, a source of high frequency current supply for the coil, contact mechanism operating at predetermined intervals making and breaking the current supply at intervals corresponding with the heating and cooling time required for tempering the tool. 3. In a tempering furnace for tools, a coreless inductor electric furnace coil having a of it.

. within the compartments f comprising a plurality of space Within the coil for insertion of a tool1 a source of high frequency current supply for the coil, relatively timed contact ma lng and breaking mechanism closing and opening the supply circuit at intervals corresponding with the heatin and cooling time reuired for temperin t e tool and a non-oxi izing atmosphere a out the tool during treatment 4. An induction electric furnace for heating tools, comprising a coreless inductor furnace coil having approximately the interior shape and dimension of the tool, means for inserting a non-oxidizing atmosphere about the tool and automatic means for connecting and disconnecting current supply with the coil to space the current connections by a time sufficient for cooling, removal and replacement of the tools.

5. A gang drill-shank-annealing furnace,

parallel compartments, electric furnace coreless inductor coils a source of high frequency current supply for the coils, a holder for the drills, maintaining them in relative positions corresponding to the positions of the compartments and means for connecting and disconnecting the electric current to and from the coils. A

6. In a gang annealing furnace for drill Shanks, a plurality of coreless inductor furnaces closed at the top and having openings at the bottom, means for inserting a nonoxidizing atmosphere Within the furnaces and a drill holder exposing the shanks and holding the drills in relative positions corresponding to the positions of the furnaces, whereby the drills may be inserted into and removed from the bottom openings Without loss of the atmosphere within the furnaces.

7. A high frequency induction electric fur` nace comprising a plurality of furnace chambers having bottom openings and an inductor coil within each chamber the bottom openings acting as guides to space the drills from the inductor coils, a holder for the drills maintaining them in relative positions corresponding With the positions of the openings and means for inserting a non-oxidizing atmosphere Within the chambers.

OVILA JOSEPH BLANCHET. 

